SiC and GaN Introduces New Testing Challenges

Floating differential measurements (such as high-side Vgs) are difficult or impossible to make due to high frequency (fast turn ons and turn offs), and the presence of high common mode voltages (such as Vds) because oscilloscope probes do not have sufficient common mode rejection at high bandwidth. The poor common mode rejection leads to the measurement being dominated by the common mode error instead of the actual differential signal. These issues can be easily resolved using Tekronix’s IsoVu isolated probes that do not de-rate with frequency at the operating requirements of GaN and SiC devices, allowing you to make accurate differential measurements. With IsoVu, you can precisely calculate and prove conduction losses, dead time losses, and switching losses.

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When evaluating new power converters that rely on SiC or GaN technology with faster switching frequencies, you will face the challenge of simultaneously monitoring multiple signals, in addition to working on the controls and timing circuitry of the converter. For example, you’ll be measuring high side Vgs, low side Vgs, high side Vds, low side Vgs, Id, IL and Iload, and control signals. You may also need to measure low voltage signals (Vgs) signals in the presence of high voltage signals (Vds). An oscilloscope with a high channel count and high vertical resolution can solve your problems.

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High resolution, multiple acquisition averaging, and complex waveform math are required in order to make accurate, repeatable switching and conduction loss measurements on high frequency SiC and GaN devices. Even measurements such as power quality, harmonics, safe operating area, and switching losses require a level of automation in the measurement process to all the information you require. Tektronix’s 5 Series MSO oscilloscopes with the 5-PWR option and probing solutions provide the automated measurement capabilities you require during design development and debug.

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With the demand for improving power efficiency and extending the operating time of battery-powered devices, engineers are switching to SiC and GaN from traditional silicon for their designs. The ability to analyze power loss and optimize power supply efficiency is more critical than ever before. One of the key factors in efficiency is the loss in switching devices. For example, a typical switch-mode power supply might have an efficiency of about 87%, meaning that 13% of the input power is dissipated within the power supply, mostly as waste heat. Of this loss, a significant portion is dissipated in the switching devices, usually MOSFETs or IGBTs. Tektronix makes it easy with the 5 and 6 Series MSO oscilloscopes and automated power analysis software to make switching loss measurements.

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